This invention relates to a shoe return spring for drum-type brakes and more aprticularly to an improved spring configuration for such a purpose.
In drum-type brakes, it is well known that relatively strong return springs are required for drawing the brake shoes back out of engagement with the brake drum when the brake is released. A wide variety of return spring arrangements have been proposed for this purpose and one popular type of return spring, which is used in many applications, employs a formed generally C-shaped spring that has its end portions engaged with the brake shoes for urging the brake shoes to their retracted position.
Various forms of anchoring devices have been employed for holding the intermediate portion of the return spring and those devices previously proposed have not been completely satisfactory. In one form of restraining device, the intermediate portion of the return spring is rigidly affixed to the backing plate. As a reuslt, the spring operates as two individual cantilevered springs. The disadvantage of this type of construction is that the spring rate is substantially increased and it makes assembly and servicing of the brake quite difficult because of the high forces on the brake shoes. The return spring may also exert uneven return forces on the shoes which will, in turn, result in uneven application forces.
It is, therefore, a principle object of this invention to provide an improved return spring arrangement for a drum-type brake that embodies a formed spring.
It is a further object of this invention to provide an improved anchoring arrangement for the intermediate portion of a formed return spring for a drum-type brake.
It is another object of this invention to provide a formed return spring for a drum brake and an anchoring system for it that will facilitate installation and removal of the brake shoes.
In connection with the mounting and return spring arrangement for drum-type brakes, it is essential that the brake shoes be mounted in such a way that they move parallel to the backing plate so that they will move into full face engagement with the brake drum. This parallel movement is necessary to insure even lining wear and full stopping forces. Certain types of return spring mechanisms may, in fact, create forces on the brake shoes that tend to cause them to move in a non-parallel relationship.
It is, therefore, a still further object of this invention to provide an improved spring arrangement and cooperation with the brake shoes of a drum-type brake wherein the brake shoes are restrained so as to move in a direction parallel to the backing plate.
It is a still further object of this invention to provide an improved return spring arrangement and supporting construction for the shoes of a drum-type brake wherein the spring assists in holding the brake shoes parallel to the backing plate.
In connection with the servicing of drum-type brakes, it is well known that the high force of the return springs makes it difficult to remove and install the brake shoes. These problems are particularly acute in conjunction with brakes employing form-type springs wherein the spring is rigidly held between its ends to the backing plate due to the high spring forces as aforenoted.
It is, therefore, a still further object of this invention to provide an improved spring arrangement for a drum-type brake wherein servicing of the brake shoes is facilitated.
In connection with the construction and assembly of drum-type brakes, it is well known that there are a number of components required for the efficient and effective operation of the brake. Frequently, the mounting of all of these components can complicate and make difficult the service of the brake assembly. For example, it is a common practice to employ a dirt shield that is fixed somehow to the backing plate of the brake and which cooperates with the periphery of the brake drum so as to prevent the ingress of foreign material into the interior of the brake. However, previously proposed arrangements for assembling all of the components including the dirt shields have resulted in complex construction.
It is, therefore, a still further object of this invention to provide an improved and simplified arrangement for mounting a dirt shield to a drum-type brake.